The Why Factor

In the West, teenagers are commonly perceived as being volatile, moody and often seen as being “trouble”. Why? Well, because they are teenagers. All that growing, all those changes. But in recent years scientists have discovered that changes to the brain, which occur during puberty, make young people less able to control their emotions and result in different attitudes towards risk as compared to adults. Can these changes to the brain explain why adolescence can be such a difficult period of our lives? Or is adolescence a manufactured cultural concept we’ve invented? (Image: Three teenagers smiling. Credit: Think Stock)

Why do we touch each other? And how do different cultures view physical contact in everyday life? Mike Williams explores our least-studied sense and meets a woman who gets her fill of human contact by cuddling people she has just met. (Image: A mother and daughter hold hands. Credit: Getty Images)

Ahead of the Sochi Winter Olympics next month and the controversy surrounding Russia’s anti-gay laws, Mike Williams and a panel of guests discuss homosexuality. Essentially, why does it exist? Is there any evolutionary advantage? And what is the current thinking in the nature vs nurture debate?(Image: A participant unfolds a rainbow flag during a local annual gay pride parade. Credit: AFP/Getty Images)

From sub Saharan Africa to the west coast tribes of Canada to the Mardi Gras of Rio, New Orleans and Venice, masks define realities - of religious belief, of healing power, of theatre and entertainment, of concealment and of memorialisation in death. They have been around as long as humanity and they evoke both fascination and fear. Mike Williams traces the power and culture of masks and asks why we have them and what they mean for us.(Image: A group wearing masks of legendary heroes as they perform a dance in Minhe County of Qinghai Province, north-west China. Credit: Getty Images)

Alcohol has been part of human civilisation for thousands of years. Evidence from pottery residues suggests that people in ancient China may have been enjoying the delights of wine as long ago as 9,000 years. But our attraction to the ethanol molecule may go back much further than that – to a time when our distant ancestors were eating nothing but fruit. So why do we drink the stuff? And why do some people have problems controlling their drinking?(Image: Scenes of debauchery and drunkenness in "Gin Lane and Beer Street" London, circa 1751. Credit: Getty Images)

Running is experiencing an explosion in popularity in the UK and across the world. So why are we running now more than ever - the recession, the Olympic competitive factor, the new social media app revolution, public health awareness, mid-life crises or rising life expectancy? Mike Williams, not exactly a natural runner, tests out these theories and is persuaded to try barefoot running himself.

Why has one of the world’s most important scientists been forgotten? Fritz Haber was the brilliant German Jewish chemist who used nitrogen to help feed billions, but arguably, kill millions. He worked with something without which, we'd all be dead. It's in our DNA and the plants we eat could not exist without it. Find out why with Mike Williams.(Image: Fritz Haber Photo by Topical Press Agency/Getty Images)

Mike Williams finds out how the way we lend and borrow money is changing. He travels to Blackpool to meet 71-year-old Jeannette, whose life was ruined by debt. He speaks to David Graeber, author of Debt: The First 5000 Years, and learns about a ground breaking debt collection service that finds people jobs before asking for their money.(Image: A man holding US $100 bank notes. Credit: Corbis)

Why do men cross dress? Mike Williams interviews Helen, a London Underground train driver, Peter a detective novelist - who prefers dressing as Penny - and Peter’s wife who helps to choose the clothes and decide Penny’s look. He talks to the artist Grayson Perry about the relationship between his art and cross dressing. He also poses the question why is it that western society accepts men in kilts, priests in cassocks but has issues with men in skirts?(Image: Artist Grayson Perry walking down the catwalk during a fashion show, in London. Credit: Getty Images)

Crying emotional tears is uniquely human. We cry over almost anything and for almost any reason – from tears of sadness to tears of joy. Music can induce them, films, stories and television news too. We do not produce tears when we are first born – it takes a few months until we are able to. But once we can, we do it right up until our final days. So why do we cry? Mike Williams traces some of the competing theories of tears with the help of scientists, psychologists, and a historian. He also watches as an actress is made to cry by her acting coach.(Image: A tear drops falls from a person's eye . BBC copyright)